Fixed Number of Heartbeats per Life

Victor Niederhoffer has a post on the fixed heartbeat theory of life: all organisms have approximately the same number of heartbeats per life. If we measure the heart rate of a mouse and multiply it by the lifespan, we get a number that is similar for most other mammals, whether horse, cow, cat, dog or guinea pig. This is related to the hypothesis that the total amount of oxygen 'processed' is constant, and the oxidative stress from this causes the cells to break down. This is because 'free-radicals' are produced in oxidation, and these molecules do damage to DNA and other essential cellular machinery.

Evidence for this was also shown by exposing nematodes to warmer environments, or drosphilia to more food, both of which sped up their metabolism, and shortened their lives (and vice versa).

All kind of neat, but bats live for 20 years, despite having a basal metabolic rate like a mouse, which lives for about 3 years. Pigeons have the same BMR as rats, yet live 10 times longer. Then there are hummingbirds which have incredibly high heartbeats and metabolism, yet live 10 years.

The key for long life is thus oxidative stress, but this is not merely a function of metabolism, but the efficiency of metabolism, and the amount of repair within the cell. Birds have very efficient mitochondria, relatively little leakage of oxidants like hydrogen peroxide in the process, compared to mammals. There are mutation repair genes, and enzymes that are very effective at getting rid of radicals (eg, Superoxide dimutase).

This gets to understanding how to improve, or change complex systems. A simple correlation between total metabolism and life, might suggest that one should focus on eating less, being leaner. All good in small doses, but too little energy is hardly an attractive payoff, as expending energy is part of a vibrant life. More practically, assuming one is in relatively lean shape, one should focus research on aiding our production of anti-oxidants and gene repair mechanisms (such as telomerase, which repairs the telomeres). See Oxygen, by Nick Lane.

Most things are pieces of complex systems, and while simple correlation suggest more is better, this does not not actually work: education, health care, more information in mortgage contracts. Invariably, trying to increase theses without consideration of the whole won't work, because the system has a delicate balance. Sometimes, the most effective part to exogenously alter is not the most obvious; it often promises, alas, modest improvement. But these are much more realistic. I think a more explicit description of one's assets would be useful. It wouldn't erase the problem, but I'm still dumbfounded by the amount of AAA rated paper on bank's balance sheets, as this was clearly a sign of bad internal pricing.